The present invention relates to weatherstrips for automobile and truck doors, windows and the like. In particular, it relates to weatherstrips made of closed cell neoprene rubber which is molded into the shape of the strip. Closed cell neoprene is considered to be the most desirable weatherstrip material since it has good flexibility and good resistance to aging in use.
The strip of closed cell neoprene material is usually molded with a flanged area at the ends which includes a metal insert molded in place. The metal insert is bent into the desired shape to facilitate mounting the end of the weatherstrip on the car door or the like.
For some time, efforts have been made to substitute plastic molded inserts for the metal inserts. This would save substantial fabrication costs which are involved in bending the metal plate. Numerous plastics have been suggested as metal substitutes, particularly reinforced resins and thermoset resins. Polyethylene oxide, phenolics and glass reinforced polyesters have been tried. However, due to the parameters involved in manufacturing and use of closed cell neoprene weatherstrips, these plastic substitutes have not been successful.
Turning first to the molding parameters involved, the closed cell neoprene rubber is molded at 350.degree. F. for fairly long periods of time, up to a maximum of about thirty minutes. The pressures involved are anywhere between ten to one hundred psi. During this molding, a plastic mounting insert tends to warp, making it impossible to mount the strip on the car. If it does not actually warp, it tends to take a set when it is handled while still hot. Also, the heat corrodes the plastic insert and may even cause it to deposit out on the mold surface.
Even when a plastic passes the muster in molding, it may fail in use, particularly since the parameters of use tend to require a different type of plastic than the parameters of molding. Plastics which tend to resist heat fairly well are too brittle at normal use temperatures. If the plastic is too brittle, it may crack or break when the workman is bolting it in place on the car door or body. It may break when the door is shut. The possibility of a brittle part cutting through the neoprene overcoat is also a risk. Thus, the mounting insert must have a certain degree of flexibility and flexibility tends to be inconsistent with high heat resistance.
Another use parameter is that the mounting insert must be sufficiently resistant to heat that warping is avoided in shipping or storing the parts. The temperature in box cars or truck trailers may get as high as 250.degree. F., particularly in the West and Southwest.
The various parameters have heretofore not been satisfied, even with plastics which have been specifically suggested as metal substitutes. Numerous failures in attempting to substitute plastics advertised as metal substitutes have plagued such substitution efforts, at least in the case of mounting inserts for weatherstrips made of closed cell neoprene.